It has long been recognized that shaving a flexible complex surface like the face with an immovable system such as the conventional razor produces nicks, cuts and lack of uniformity of shaving due to the varying face profile of the shaver. Closeness of the shave is dependent upon, among other factors, the angle of contact between face and blade as well as the flow of skin immediately preceding contact with the blade. One of the factors controlling this flow of skin is the distance between the blade edge and the surface of the blade assembly which contacts the face immediately prior to the blade edge. This distance measured by the tangential line between the face engaging points of the blade and the leading surface is known as span. In a two blade system, each blade has a separate span. The leading or bottom blade has a span determined by the tangent line drawn between its edge and the leading edge of the guard bar which is part of the blade support structure and designed to, at least in part, direct skin flow to the blade. The second blade has a span measured by a tangent line drawn between the first and second blade. In the case of the two blade system the first or bottom blade determines the skin flow to the second blade.
Several attempts have been made in the past to control the shaving properties of the blade assembly by providing the blade assembly with flexible or moveable components in various combinations. U.S. Pat. No. 4,516,320 issued May 14, 1985 to Anthony J. Peleckis discloses a blade assembly with flexible blades and spacer which move downward in response to shaving forces and the guard bar which flexes inward and upward.
U.S. Pat. No. 4,443,939 issued to Vincent C. Motta and Ernest F. Kiraly on Apr. 24, 1984 describes a blade assembly in which a cap and guard bar as well as blades and spacer are flexible and tend to conform to the facial curves of shaving pressures applied.
U.S. Pat. No. 4,069,580 issued to Cyril A. Cartwright et al issued Jan. 24, 1978 and U.S. Pat. No. 4,409,735 also issued to Cartwright et al on Oct. 18, 1983 disclose a flexible razor produced by utilizing a flexible guard bar and flexible cap as well as flexible blades and spacers. A series of ten patents issued to Chester F. Jacobson U.S. Pat. No. 4,587,729 issued May 13, 1986 being the latest, describes a blade assembly with blades which are individually biased move linearly reciprocally in response to shaving forces. In several of these patents, Jacobson also teaches the same type of movement for a guard bar.